(a) Field
The described technology relates generally to a display device and a touch sensing method thereof, and particularly relates to an organic light emitting device having a touch sensing function and a touch sensing method thereof.
(b). Description of the Related Art
Among display devices, since an organic light emitting diode (OLED) display as a self-light emitting type that does not require a separate light source, it is advantageous in terms of power consumption, response speed, viewing angle, and contrast ratio.
The organic light emitting diode (OLED) display includes a plurality of pixels such as red pixels, blue pixels, green pixels, and white pixels, and may express full colors by combining the pixels. Each pixel includes a light emitting element, and a plurality of thin film transistors for driving the light emitting element.
The light emitting element of the organic light emitting diode (OLED) display includes a pixel electrode, a common electrode, and an emission layer positioned between the two electrodes. One of the pixel electrode and the common electrode becomes an anode and the other becomes a cathode. Electrons injected from the cathode and holes injected from the anode are coupled with each other in the light emitting layer to form excitons, and the excitons emit light while discharging energy. The common electrode is formed throughout a plurality of pixels to transmit a predetermined common voltage.
The OLED display may be divided into a bottom emission type in which light is emitted to the bottom of a substrate and a top emission type in which light is emitted to the top of the substrate. In the case of the top emission type of OLED display, the common electrode may be made of a transparent conductive material.
On the other hand, recently, a display device having a function of sensing external touch of a finger, etc., of a person has been actively developed. The external touch sensing function means a function in which it is capable of sensing touch information such as a touch existence and a touch position when an external object such as the finger or a touch pen approaches or contacts a screen. This function may allow a machine such as a computer, etc., to perform a desired command by touching a finger or a touch pen (or stylus) to a screen of the touch panel to write or draw characters or execute icons.
In this instance, a glass substrate for a touch may be formed on a substrate to provide the touch sensing function to the bottom emission type of organic light emitting device. However, the organic light emitting device becomes thicker and heavier because of the glass substrate used for a touch.